Thermal Consideration and Design for a 200-kW SiC-Based High-Density Three-Phase Inverter in More Electric Aircraft

Thermal management is important since it determines the reliability and robustness of power inverters. It becomes more critical for high-altitude motor drives due to the reduced air density. This paper provides a design process of thermal management for high-density high-power inverters. Thermal models for different scenarios are derived, and the hotspot temperature can be estimated under different cooling conditions. To demonstrate the proposed design process, a 200 kW three-level T-Type propulsion inverter designed for altitude of 7,620 m (25,000 ft) is used to present the thermal designs. Several thermal mitigation techniques are also introduced. In addition, it is discovered that the stagnating air space can create hotspots and have detrimental effect on the thermal performances. To address the thermal issue of stagnating air space, several solutions are proposed in which the forced cooling air duct solution is selected in this work. By optimizing both internal and external airflow, the hotspot temperature in the stagnating air space is reduced by 41 % using designed air duct. Furthermore, based on full-power experimental thermal tests, the hotspot temperature of inverter within sealed enclosure can be maintained lower than 130 °C at the ambient of 75 °C and altitude of 7,620 m. The final thermal design verifies the feasibility of the proposed design process.